Field of the Invention
The present invention relates to a vibration-type actuator, and an image pickup apparatus and a stage each including the same.
Description of the Related Art
There are various vibration-type actuators (for example, an oscillatory wave motor) in each of which a driven member is driven with vibrations generated in an elastic member. In an oscillatory wave motor, a vibrator including an electromechanical energy conversion element (such as a piezoelectric element) and an elastic member (mostly, a metal elastic member) that is bonded to the electromechanical energy conversion element is excited to vibrate in a plurality of vibration modes. With the combination of the plurality of vibration modes, the surface of the elastic member undergoes an elliptic movement, whereby the driven member that is in contact with the elastic member is driven relative to the elastic member. Various kinds of such oscillatory wave motors have been proposed. For example, known oscillatory wave motors that rotationally drive lens barrels included in cameras and the like include a ring-shaped oscillatory wave motor, a bar-type rotary oscillatory wave motor, and so forth. Many other motors with improvements in their configurations or forms have also been proposed, such as an oscillatory wave motor in the form of a rotary actuator that includes a plurality of flat-plate elastic members each having a thin-plate vibrating portion and a projecting portion, the elastic members being arranged along the circumference of the motor. In addition, many vibration-type linear actuators have been proposed in each of which a flat-plate elastic member, such as the one described above, is provided in contact with a linear slider in such a manner as to be driven linearly.
An outline of an exemplary oscillatory wave motor, disclosed by Japanese Patent Laid-Open No. 2011-200053, including a flat-plate elastic member will now be described. The oscillatory wave motor includes a vibrator and a slider that is in contact with the vibrator. The vibrator includes an elastic member and a piezoelectric element. The piezoelectric element is bonded to the elastic member with adhesive or the like. The elastic member includes a vibrating portion that vibrates together with the piezoelectric element, a supported portion that is substantially insulated from vibration generated in the vibrating portion, and a connecting portion that connects the vibrating portion and the supported portion to each other, the connecting portion functioning such that one end thereof follows the vibration of the vibrating portion while the other end thereof suppresses the transmission of the vibration to the supported portion. The vibrating portion has, on one surface thereof, two projecting portions via which the vibration is transmitted to a driven member. When alternating-current electric fields with different phases are applied to the piezoelectric element, the vibrator is excited to generate two kinds of out-of-plane bending vibrations, whereby the tips of the two projecting portions each undergo an elliptic movement. Consequently, the slider that is in contact with the projecting portions receives a frictional driving force and is thus driven in one direction.
Meanwhile, Japanese Patent Laid-Open No. 64-34184 discloses an ultrasonic motor in which the entirety of a vibrator is supported by a supporting member with vibration-isolating members interposed therebetween, whereby the loss of vibrational energy is reduced.